In many packet-oriented communication networks, such as the Internet, no performance is guaranteed for connections between terminals in these communication networks if no additional precautions are taken. The performance of a connection is also frequently known as “Quality of Service” (QoS) and can include different transmission and connection resources, such as the transmission bandwidth, the transmission rate, the permissible error rate and/or the transmission duration.
In up-to-date communication systems, which are frequently based on such packet-oriented communication networks, resource managers are provided in order to ensure a predetermined performance. In each case these are assigned to a communication network or subnetwork in order to manage its transmission resources. When there is a resource manager, transmission resources which can be predetermined specifically for connections can be reserved for the connections which have to be established. Following a successful reservation of transmission resources, the resource manager monitors the continuous availability of the reserved transmission resources for the connection concerned.
Usually when a connection needs to be established, its origin and destination are transmitted to a resource manager so that it can reserve the necessary transmission resources. The resource manager then uses the transmitted origin and destination information to determine the path over which the connection needing to be established will run. To do this according to known related art, the resource manager needs precise information about the complete topology of the communication network. This information is transmitted to the resource manager very expensively with the aid of a routing protocol. A method of this kind is described in the document “Performance of QoS Agents for Provisioning Network Resources” by Schelén et al. in the Proceedings of IFIP Seventh International Workshop on Quality of Service (IWQoS'99), London, June 1999.
In many cases connections need to be established between different subnetworks in a communication system, for which purpose the subnetworks themselves may well have a very large transmission bandwidth, but are coupled over a transmission path with a proportionately narrow transmission bandwidth. A typical example of this is when local area networks (LANs) are coupled over a public telephone network. In this case the telephone network with its proportionately narrow transmission bandwidth represents a bottleneck for data needing to be exchanged between the local area networks. This leads to the problem of how to control transmission resources efficiently even for connections running through such bottlenecks.